The present disclosure relate generally to containment devices, including but not limited to medical devices, such as implantable medical devices, having containment reservoirs for confining substance or subcomponents for later exposure or release. In particular, the present disclosure relates to improved containment devices and methods of manufacture thereof, including but not limited to space-efficient device assemblies, as well as improved methods for making microchip containment device elements.
Typical implantable medical devices such as pacemakers and implantable cardioverter defibrillators are designed with two or more housing components or shells that contain the control electronics, power source and other device specific components. A header is also used to provide electrical connections into and out of the device. The housing and header or feedthrough are designed to be hermetic to prevent liquid or gas exchange between the internal components, which are typically not biocompatible, and body fluids. It is noted, however, that certain implants with epoxy based headers that do not achieve long term hermeticity. Design and manufacturing methods of implantable devices have evolved with the goal of ensuring hermeticity.
MicroCHIPS Inc. designs and manufactures implantable devices based on microchips which include reservoir arrays containing biosensors or drugs. FIG. 1 shows a possible conventional approach for assembly of components in an implantable medical device 10, which includes a microchip assembly 12. The microchip assembly 12, which is also referred to as a microchip element, includes microreservoirs, each of which may contain a drug for controlled delivery in vivo or a sensor for controlled exposure in vivo. The microchip assembly 12 is attached to a feedthrough 16 that is welded to the housing 14. Such microchip assemblies or elements are described, for example, in U.S. Pat. No. 7,510,551 to Uhland et al. and U.S. Pat. No. 7,604,628 to Santini Jr. et al. The feedthrough 16 contains electrically conductive pins that are metallurgically brazed to metallized surfaces on and through an alumina disc. A typical pin count exceeds 100, and in more complex designs, can be over 400. The consequence of such designs is that each pin connection can be a leak point.
In addition, each feedthrough pin is electrically connected to an electronic component inside the housing. Some designs utilize a wire from the pin to the circuit, while the illustrated design attaches the feedthrough 16 directly to a conventional plastic circuit board 18. These electrical connections require testing to ensure continuity. As a result, the pin count impacts the cost of the feedthrough, and that cost increases as the number of feedthrough pins increases in the implantable device. Consequently, due to this complex design requirement, the resulting manufacturing, and the required acceptance tests, the feedthrough is an expensive component.
Another disadvantage of conventional implantable device designs based on a feedthrough or header attached to housing components is that the overall volume of the resulting device is larger than desired, because several discrete components make up the assembly.
Furthermore, electronic-based implantable devices that use radio frequency to wirelessly transfer information in and out of the body require an antenna. Radio frequency waves are significantly attenuated when the antenna is placed in a conventional metallic housing, and therefore, the antenna typically is placed on the surface of the housing, utilizing the existing feedthrough or another feedthrough dedicated for this application.
It therefore would be desirable to eliminate or mitigate any or all of the foregoing disadvantages associated with conventional designs of implantable medical devices. In one particular need, it would be desirable to provide improved housing hermeticity (e.g., fewer potential leak paths), simpler construction, and a smaller overall device volume.
In another aspect, in making microchip-based reservoir devices, such as taught in U.S. Pat. No. 7,604,628 to Santini Jr. et al., it would be desirable to provide greater reservoir volumes using precision manufacturing methods that are easier and more cost effective to use. For example, it would be useful to reduce or eliminate the need to use DRIE (deep reactive ion etching) processes to form the walls defining the micro-reservoirs in the microchip element.